我通过javascript突出显示的当前日期显示不正确

在堆栈溢出的帮助下，我成功地完成了从2015年5月到10月底的日历循环。现在我想强调一下目前的日期是6月28日星期日。但由于某种原因，它突出显示了错误的日期，我不认为这是因为代码，但我不能100%确定。

签出此链接以直观地查看(http://gyazo.com/30e448d0f84c8f1c55e4dd1ce6d91f38)

jsfiddle链接：https://jsfiddle.net/GY22/vqfk8yLL/

这是我的html代码：

<ul id="timeline">
    <li></li>
</ul>

这是我的javascript代码：

<script>
// Get today's current date.
var now = new Date();
console.log(now);
// Calculates the number of the week
var weekNumber = ((now.getDate()<10) ? "0" : "")+ now.getDate();
console.log("The current week number is: " + weekNumber);
// Array list of months.
var month = new Array(12);
month[0] = "January";
month[1] = "February";
month[2] = "March";
month[3] = "April";
month[4] = "May";
month[5] = "June";
month[6] = "July";
month[7] = "August";
month[8] = "September";
month[9] = "October";
month[10] = "November";
month[11] = "December";
//console.log(month[3]);
var weekDay = new Array(7);
weekDay[0]=  "Su";
weekDay[1] = "Mo";
weekDay[2] = "Tu";
weekDay[3] = "We";
weekDay[4] = "Th";
weekDay[5] = "Fr";
weekDay[6] = "Sa";
function formatDate(date) {
    var month = date.getUTCMonth() +1;
    var dayNumber = date.getUTCDate();
    var year = date.getUTCFullYear();
    var day = date.getUTCDay();
    return weekDay[day] + ": " + dayNumber + "-" + month + "-" + year + ";  ";
    //return weekDay[day] + " " + dayNumber + ";  "; 
}
//console.log(formatDate(new Date()));
var today
function addListItem(){
    var createListItem = document.createElement("li");
    var outputListItem = document.createTextNode(today);
    createListItem.appendChild(outputListItem);
    var createUl = document.getElementsByTagName("ul");
    createUl[0].appendChild(createListItem);
}
// loop starting from may up untill for months from the set date
for (var i = 0; i < 122; i++){
    today = formatDate(new Date(2015, 05, i));
    //document.write(today + "<br />");
    addListItem();
}
document.getElementById('timeline').
getElementsByTagName('li')[(new Date()).getDate() - 1].className += ' currentDate';